Regensburg 2022 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 41: Organic Semiconductors 2
HL 41.2: Vortrag
Freitag, 9. September 2022, 09:45–10:00, H34
Regiochemistry of Donor-Dendrons Controls the Performance of TADF Dendrimer based OLEDs — •Rishabh Saxena1, Dianming Sun2, Stavros Athanasopoulos1, Eli Zysman-Colman2, and Anna Köhler1 — 1University of Bayreuth, Germany — 2University of St. Andrews, UK
The potential of dendrimers exhibiting thermally activated delayed fluorescence (TADF) as emitters in solution-processed organic light-emitting diodes (OLEDs) has to date not yet been realized. This in part is due to a poor understanding of the structure-property relationships in dendrimers where reports of detailed photophysical characterization and mechanism studies are lacking. In this study, we investigated dendrimers with multiple dendritic electron-donating moieties connected to a central electron-accepting core via a para- or a meta-phenylene bridge. Characterization of host-free OLEDs revealed the superiority of meta-dendrimers as compared to the already reported para-analogue. Photophysical investigations in the films showed that, although all the dendrimers possess similar singlet-triplet energy gap, normally implying similar reverse intersystem crossing (RISC) rate, better TADF properties are obtained for meta-dendrimers when compared to para-dendrimers. In this regard, what this study reveals is that the reorganization energy can play an important role in enhancing RISC rate and that this can be modulated as a function of the regiochemistry of donor dendron about the acceptor. This is a heretofore unexploited strategy and can be used as a general chemical design principle, especially in the case of bulky dendrimers.